Apparatus and methods for oscillation suppression of cascode power amplifiers

ABSTRACT

Apparatus and methods for oscillation suppression of cascode power amplifiers are provided herein. In certain implementations, a power amplifier system includes a cascode power amplifier including a plurality of transconductance devices that operate in combination with a plurality of cascode devices to amplify a radio frequency input signal. The power amplifier system further includes a bias circuit that biases the plurality of cascode devices with two or more bias voltages that are decoupled from one another at radio frequency to thereby inhibit the cascode power amplifier from oscillating.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119(e)of U.S. Provisional Patent Application No. 62/477,011, filed Mar. 27,2017 and titled “APPARATUS AND METHODS FOR OSCILLATION SUPPRESSION OFCASCODE POWER AMPLIFIERS,” which is herein incorporated by reference inits entirety.

BACKGROUND Field

Embodiments of the invention relate to electronic systems, and inparticular, to radio frequency (RF) electronics.

Description of the Related Technology

Power amplifiers can be used to boost or amplify a radio frequency (RF)signal. Thereafter, the boosted RF signal can be used for a variety ofpurposes, including, for example, driving an antenna of an RFcommunication system.

Power amplifiers can be included in a wide variety of communicationdevices, including, but not limited to, mobile phones, tablets, basestations, network access points, laptops, computers, and televisions.Power amplifiers provide amplification to RF signals, which can have afrequency in the range from about 450 MHz to about 90 GHz for certaincommunication standards.

SUMMARY

In certain embodiments, the present disclosure relates to a poweramplifier system. The power amplifier system includes an input terminalconfigured to receive a radio frequency input signal, an outputterminal, and a cascode power amplifier including a plurality oftransconductance devices each electrically coupled to the inputterminal, and a plurality of cascode devices each electrically coupledto the output terminal. The plurality of transconductance devices areconfigured to operate in combination with the plurality of cascodedevices to amplify the radio frequency input signal. The power amplifiersystem further includes a bias circuit configured to bias the pluralityof cascode devices with two or more bias signals that are decoupled fromone another at radio frequency so as to provide oscillation suppressionto the cascode power amplifier.

In some embodiments, the two or more bias signals include a plurality ofbias voltages operable to separately bias the plurality of cascodedevices. According several embodiments, the power amplifier systemfurther includes two or more biasing conductors configured to separatelyroute the two or more bias signals to the plurality of cascode devices.In accordance with a number of embodiments, each of the two or morebiasing conductors are physically and electrically disconnected from oneanother.

In various embodiments, the two or more bias signals includes a firstbias voltage configured to bias a first portion of the plurality ofcascode devices and a second bias voltage configured to bias a secondportion of the plurality of cascode devices. In accordance with a numberof embodiments, the two or more bias signals further includes a thirdbias voltage configured to bias a third portion of the plurality ofcascode devices. According to several embodiments, the power amplifiersystem further includes a radio frequency isolation circuit electricallycoupled between the first bias voltage and the second bias voltage.

In some embodiments, the plurality of transconductance devices include aplurality of common emitter bipolar transistors.

In a number of embodiments, the plurality of transconductance devicesinclude a plurality of common source field-effect transistors.

In several embodiments, the plurality of cascode devices include aplurality of common gate field-effect transistors.

In various embodiments, the plurality of cascode devices include aplurality of common base bipolar transistors.

In some embodiments, the bias circuit includes a plurality of sourcefollower field-effect transistors configured to bias the plurality ofcascode devices with a plurality of bias voltages that are decoupledfrom one another at radio frequency.

In several embodiments, the bias circuit includes a plurality of emitterfollower bipolar transistors configured to bias the plurality of cascodedevices with a plurality of bias voltages that are decoupled from oneanother at radio frequency.

In various embodiments, the power amplifier system further includes achoke inductor electrically connected between a supply voltage and theoutput terminal, the choke inductor configured to provide the supplyvoltage to the plurality of cascode devices.

In some embodiments, the bias circuit is further configured to bias theplurality of transconductance devices with a common bias signal.

In several embodiments, the power amplifier system further includes aplurality of degeneration circuits electrically coupled between theplurality of transconductance devices and ground. In accordance with anumber of embodiments, the plurality of degeneration circuits include aplurality of degeneration resistors.

In various embodiments, the bias circuit includes a plurality of ACgrounding capacitors electrically connected between the plurality ofcascode devices and ground.

In certain embodiments, the present disclosure relates to a packagedmodule. The packaged module includes a package substrate, and asemiconductor die attached to the package substrate. The semiconductordie includes an input terminal configured to receive a radio frequencyinput signal, an output terminal, and a cascode power amplifierincluding a bias circuit, a plurality of transconductance devices eachelectrically coupled to the input terminal, and a plurality of cascodedevices each electrically coupled to the output terminal. The pluralityof transconductance devices are configured to operate in combinationwith the plurality of cascode devices to amplify the radio frequencyinput signal. Additionally, the bias circuit is configured to bias theplurality of cascode devices with two or more bias signals that aredecoupled from one another at radio frequency so as to provideoscillation suppression to the cascode power amplifier.

In some embodiments, the two or more bias signals include a plurality ofbias voltages operable to separately bias the plurality of cascodedevices. In accordance with a number of embodiments, the semiconductordie further includes two or more biasing conductors configured toseparately route the two or more bias signals to the plurality ofcascode devices. According to several embodiments, each of the two ormore biasing conductors are physically and electrically disconnectedfrom one another.

In various embodiments, the two or more bias signals includes a firstbias voltage configured to bias a first portion of the plurality ofcascode devices and a second bias voltage configured to bias a secondportion of the plurality of cascode devices. According to a number ofembodiments, the two or more bias signals further includes a third biasvoltage configured to bias a third portion of the plurality of cascodedevices. In accordance with several embodiments, the cascode poweramplifier further includes a radio frequency isolation circuitelectrically coupled between the first bias voltage and the second biasvoltage.

In some embodiments, the plurality of transconductance devices include aplurality of common emitter bipolar transistors.

In a number of embodiments, the plurality of transconductance devicesinclude a plurality of common source field-effect transistors.

In several embodiments, the plurality of cascode devices include aplurality of common gate field-effect transistors.

In various embodiments, the plurality of cascode devices include aplurality of common base bipolar transistors.

In some embodiments, the bias circuit includes a plurality of sourcefollower field-effect transistors configured to bias the plurality ofcascode devices with a plurality of bias voltages that are decoupledfrom one another at radio frequency.

In several embodiments, the bias circuit includes a plurality of emitterfollower bipolar transistors configured to bias the plurality of cascodedevices with a plurality of bias voltages that are decoupled from oneanother at radio frequency.

In various embodiments, the semiconductor die further includes a chokeinductor electrically connected between a supply voltage and the outputterminal, the choke inductor configured to provide the supply voltage tothe plurality of cascode devices.

In a number of embodiments, the bias circuit is further configured tobias the plurality of transconductance devices with a common biassignal.

In some embodiments, the cascode power amplifier further includes aplurality of degeneration circuits electrically coupled between theplurality of transconductance devices and ground. In accordance withseveral embodiments, the plurality of degeneration circuits include aplurality of degeneration resistors.

In a number of embodiments, the bias circuit includes a plurality of ACgrounding capacitors electrically connected between the plurality ofcascode devices and ground.

In certain embodiments, the present disclosure relates to a wirelesscommunication device. The wireless communication device includes atransmitter configured to generate a radio frequency signal. Thewireless communication device further includes a cascode power amplifiersystem including an input terminal configured to receive the radiofrequency signal, an output terminal, a bias circuit, a plurality oftransconductance devices each electrically coupled to the inputterminal, and a plurality of cascode devices each electrically coupledto the output terminal. The plurality of transconductance devices areconfigured to operate in combination with the plurality of cascodedevices to amplify the radio frequency signal to thereby generate anamplified radio frequency signal. Additionally, the bias circuit isconfigured to bias the plurality of cascode devices with two or morebias signals that are decoupled from one another at radio frequency soas to provide oscillation suppression. The wireless communication devicefurther includes an antenna configured to receive the amplified radiofrequency signal.

In some embodiments, the wireless communication device further includesa switch, and the antenna is electrically connected to the outputterminal of the cascode power amplifier system via the switch.

In various embodiments, the two or more bias signals include a pluralityof bias voltages operable to separately bias the plurality of cascodedevices. In accordance with several embodiments, the cascode poweramplifier system further includes two or more biasing conductorsconfigured to separately route the two or more bias signals to theplurality of cascode devices. According to a number of embodiments, eachof the two or more biasing conductors are physically and electricallydisconnected from one another.

In various embodiments, the two or more bias signals includes a firstbias voltage configured to bias a first portion of the plurality ofcascode devices and a second bias voltage configured to bias a secondportion of the plurality of cascode devices. According to a number ofembodiments, the two or more bias signals further includes a third biasvoltage configured to bias a third portion of the plurality of cascodedevices. In accordance with several embodiments, the cascode poweramplifier system further includes a radio frequency isolation circuitelectrically coupled between the first bias voltage and the second biasvoltage.

In some embodiments, the plurality of transconductance devices include aplurality of common emitter bipolar transistors.

In various embodiments, the plurality of transconductance devicesinclude a plurality of common source field-effect transistors.

In a number of embodiments, the plurality of cascode devices include aplurality of common gate field-effect transistors.

In several embodiments, the plurality of cascode devices include aplurality of common base bipolar transistors.

In some embodiments, the bias circuit includes a plurality of sourcefollower field-effect transistors configured to bias the plurality ofcascode devices with a plurality of bias voltages that are decoupledfrom one another at radio frequency.

In a number of embodiments, the bias circuit includes a plurality ofemitter follower bipolar transistors configured to bias the plurality ofcascode devices with a plurality of bias voltages that are decoupledfrom one another at radio frequency.

In various embodiments, the cascode power amplifier system furtherincludes a choke inductor electrically connected between a supplyvoltage and the output terminal, and the choke inductor configured toprovide the supply voltage to the plurality of cascode devices.

In several embodiments, the bias circuit is further configured to biasthe plurality of transconductance devices with a common bias signal.

In some embodiments, the cascode power amplifier further includes aplurality of degeneration circuits electrically coupled between theplurality of transconductance devices and ground. According to a numberof embodiments, the plurality of degeneration circuits include aplurality of degeneration resistors.

In various embodiments, the bias circuit includes a plurality of ACgrounding capacitors electrically connected between the plurality ofcascode devices and ground.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of one example of a communication network.

FIG. 2A is a schematic diagram of one example of a communication linkusing carrier aggregation.

FIG. 2B illustrates various examples of carrier aggregation for thecommunication link of FIG. 2A.

FIG. 3A is a schematic diagram of one example of a downlink channelusing multi-input and multi-output (MIMO) communications.

FIG. 3B is schematic diagram of one example of an uplink channel usingMIMO communications.

FIG. 4A is a schematic diagram of one example of a communication systemthat operates with beamforming.

FIG. 4B is a schematic diagram of one example of beamforming to providea transmit beam.

FIG. 4C is a schematic diagram of one example of beamforming to providea receive beam.

FIG. 5 is a schematic diagram of one embodiment of a power amplifiersystem with separated cascode biasing.

FIG. 6 is a schematic diagram of one embodiment of a radio frequencycommunication system.

FIG. 7A is a schematic diagram of another embodiment of a poweramplifier with separated cascode biasing.

FIG. 7B is a schematic diagram of another embodiment of a poweramplifier with separated cascode biasing.

FIG. 7C is a schematic diagram of another embodiment of a poweramplifier with separated cascode biasing.

FIG. 7D is a schematic diagram of another embodiment of a poweramplifier with separated cascode biasing.

FIG. 8A is a schematic diagram of another embodiment of a poweramplifier with separated cascode biasing.

FIG. 8B is a schematic diagram of another embodiment of a poweramplifier with separated cascode biasing.

FIG. 8C is a schematic diagram of another embodiment of a poweramplifier with separated cascode biasing.

FIG. 9 is a schematic diagram of another embodiment of a power amplifiersystem with separated cascode biasing.

FIG. 10A is a schematic diagram of one example of a power amplifiersystem with shared cascode biasing.

FIG. 10B is a schematic diagram representing high frequency operation ofthe power amplifier system of FIG. 10A.

FIG. 10C is a schematic diagram of one example of a differentialColpitts oscillator.

FIG. 11A is a schematic diagram of a front end system according to oneembodiment.

FIG. 11B is a schematic diagram of a front end system according toanother embodiment.

FIG. 12A is a schematic diagram of a wireless communication deviceaccording to one embodiment.

FIG. 12B is a schematic diagram of a wireless communication deviceaccording to another embodiment.

FIG. 13 is a schematic diagram of one embodiment of a mobile device.

FIG. 14A is a schematic diagram of one embodiment of a packaged module.

FIG. 14B is a schematic diagram of a cross-section of the packagedmodule of FIG. 14A taken along the lines 14B-14B.

DETAILED DESCRIPTION OF EMBODIMENTS

The following detailed description of certain embodiments presentsvarious descriptions of specific embodiments. However, the innovationsdescribed herein can be embodied in a multitude of different ways, forexample, as defined and covered by the claims. In this description,reference is made to the drawings where like reference numerals canindicate identical or functionally similar elements. It will beunderstood that elements illustrated in the figures are not necessarilydrawn to scale. Moreover, it will be understood that certain embodimentscan include more elements than illustrated in a drawing and/or a subsetof the elements illustrated in a drawing. Further, some embodiments canincorporate any suitable combination of features from two or moredrawings.

The International Telecommunication Union (ITU) is a specialized agencyof the United Nations (UN) responsible for global issues concerninginformation and communication technologies, including the shared globaluse of radio spectrum.

The 3rd Generation Partnership Project (3GPP) is a collaboration betweengroups of telecommunications standard bodies across the world, such asthe Association of Radio Industries and Businesses (ARIB), theTelecommunications Technology Committee (TTC), the China CommunicationsStandards Association (CCSA), the Alliance for TelecommunicationsIndustry Solutions (ATIS), the Telecommunications Technology Association(TTA), the European Telecommunications Standards Institute (ETSI), andthe Telecommunications Standards Development Society, India (TSDSI).

Working within the scope of the ITU, 3GPP develops and maintainstechnical specifications for a variety of mobile communicationtechnologies, including, for example, second generation (2G) technology(for instance, Global System for Mobile Communications (GSM) andEnhanced Data Rates for GSM Evolution (EDGE)), third generation (3G)technology (for instance, Universal Mobile Telecommunications System(UMTS) and High Speed Packet Access (HSPA)), and fourth generation (4G)technology (for instance, Long Term Evolution (LTE) and LTE-Advanced).

The technical specifications controlled by 3GPP can be expanded andrevised by specification releases, which can span multiple years andspecify a breadth of new features and evolutions.

In one example, 3GPP introduced carrier aggregation (CA) for LTE inRelease 10. Although initially introduced with two downlink carriers,3GPP expanded carrier aggregation in Release 14 to include up to fivedownlink carriers and up to three uplink carriers. Other examples of newfeatures and evolutions provided by 3GPP releases include, but are notlimited to, License Assisted Access (LAA), enhanced LAA (eLAA),Narrowband Internet-of-Things (NB-TOT), Vehicle-to-Everything (V2X), andHigh Power User Equipment (HPUE).

3GPP plans to introduce Phase 1 of fifth generation (5G) technology inRelease 15 (targeted for 2018) and Phase 2 of 5G technology in Release16 (targeted for 2019). Release 15 is anticipated to address 5Gcommunications at less than 6 GHz, while Release 16 is anticipated toaddress communications at 6 GHz and higher. Subsequent 3GPP releaseswill further evolve and expand 5G technology. 5G technology is alsoreferred to herein as 5G New Radio (NR).

Preliminary specifications for 5G NR support a variety of features, suchas communications over millimeter wave spectrum, beam formingcapability, high spectral efficiency waveforms, low latencycommunications, multiple radio numerology, and/or non-orthogonalmultiple access (NOMA). Although such RF functionalities offerflexibility to networks and enhance user data rates, supporting suchfeatures can pose a number of technical challenges.

The teachings herein are applicable to a wide variety of communicationsystems, including, but not limited to, communication systems usingadvanced cellular technologies, such as LTE-Advanced, LTE-Advanced Pro,and/or 5G NR.

FIG. 1 is a schematic diagram of one example of a communication network10. The communication network 10 includes a macro cell base station 1, asmall cell base station 3, and various examples of user equipment (UE),including a first mobile device 2 a, a wireless-connected car 2 b, alaptop 2 c, a stationary wireless device 2 d, a wireless-connected train2 e, and a second mobile device 2 f.

Although specific examples of base stations and user equipment areillustrated in FIG. 1, a communication network can include base stationsand user equipment of a wide variety of types and/or numbers.

For instance, in the example shown, the communication network 10includes the macro cell base station 1 and the small cell base station3. The small cell base station 3 can operate with relatively lowerpower, shorter range, and/or with fewer concurrent users relative to themacro cell base station 1. The small cell base station 3 can also bereferred to as a femtocell, a picocell, or a microcell. Although thecommunication network 10 is illustrated as including two base stations,the communication network 10 can be implemented to include more or fewerbase stations and/or base stations of other types.

Although various examples of user equipment are shown, the teachingsherein are applicable to a wide variety of user equipment, including,but not limited to, mobile phones, tablets, laptops, IoT devices,wearable electronics, customer premises equipment (CPE),wireless-connected vehicles, wireless relays, and/or a wide variety ofother communication devices. Furthermore, user equipment includes notonly currently available communication devices that operate in acellular network, but also subsequently developed communication devicesthat will be readily implementable with the inventive systems,processes, methods, and devices as described and claimed herein.

The illustrated communication network 10 of FIG. 1 supportscommunications using a variety of technologies, including, for example,4G LTE, 5G NR, and wireless local area network (WLAN), such as Wi-Fi.Although various examples of communication technologies have beenprovided, the communication network 10 can be adapted to support a widevariety of communication technologies.

Various communication links of the communication network 10 have beendepicted in FIG. 1. The communication links can be duplexed in a widevariety of ways, including, for example, using frequency-divisionduplexing (FDD) and/or time-division duplexing (TDD). FDD is a type ofradio frequency communications that uses different frequencies fortransmitting and receiving signals. FDD can provide a number ofadvantages, such as high data rates and low latency. In contrast, TDD isa type of radio frequency communications that uses about the samefrequency for transmitting and receiving signals, and in which transmitand receive communications are switched in time. TDD can provide anumber of advantages, such as efficient use of spectrum and variableallocation of throughput between transmit and receive directions.

In certain implementations, user equipment can communication with a basestation using one or more of 4G LTE, 5G NR, and Wi-Fi technologies. Incertain implementations, enhanced license assisted access (eLAA) is usedto aggregate one or more licensed frequency carriers (for instance,licensed 4G LTE and/or 5G NR frequencies), with one or more unlicensedcarriers (for instance, unlicensed Wi-Fi frequencies).

The communication links can operate over a wide variety of frequencies.In certain implementations, communications are supported using 5G NRtechnology over one or more frequency bands that are less than 6Gigahertz (GHz) and/or over one or more frequency bands that are greaterthan 6 GHz. In one embodiment, one or more of the mobile devices supporta HPUE power class specification.

In certain implementations, a base station and/or user equipmentcommunicates using beamforming. For example, beamforming can be used tofocus signal strength to overcome path losses, such as high lossassociated with communicating over high signal frequencies. In certainembodiments, user equipment, such as one or more mobile phones,communicate using beamforming on millimeter wave frequency bands in therange of 30 GHz to 300 GHz and/or upper centimeter wave frequencies inthe range of 6 GHz to 30 GHz, or more particularly, 24 GHz to 30 GHz.

Different users of the communication network 10 can share availablenetwork resources, such as available frequency spectrum, in a widevariety of ways.

In one example, frequency division multiple access (FDMA) is used todivide a frequency band into multiple frequency carriers. Additionally,one or more carriers are allocated to a particular user. Examples ofFDMA include, but are not limited to, single carrier FDMA (SC-FDMA) andorthogonal FDMA (OFDMA). OFDM is a multicarrier technology thatsubdivides the available bandwidth into multiple mutually orthogonalnarrowband subcarriers, which can be separately assigned to differentusers.

Other examples of shared access include, but are not limited to, timedivision multiple access (TDMA) in which a user is allocated particulartime slots for using a frequency resource, code division multiple access(CDMA) in which a frequency resource is shared amongst different usersby assigning each user a unique code, space-divisional multiple access(SDMA) in which beamforming is used to provide shared access by spatialdivision, and non-orthogonal multiple access (NOMA) in which the powerdomain is used for multiple access. For example, NOMA can be used toserve multiple users at the same frequency, time, and/or code, but withdifferent power levels.

Enhanced mobile broadband (eMBB) refers to technology for growing systemcapacity of LTE networks. For example, eMBB can refer to communicationswith a peak data rate of at least 10 Gbps and a minimum of 100 Mbps foreach user. Ultra-reliable low latency communications (uRLLC) refers totechnology for communication with very low latency, for instance, lessthan 2 milliseconds. uRLLC can be used for mission-criticalcommunications such as for autonomous driving and/or remote surgeryapplications. Massive machine-type communications (mMTC) refers to lowcost and low data rate communications associated with wirelessconnections to everyday objects, such as those associated with Internetof Things (IoT) applications.

The communication network 10 of FIG. 1 can be used to support a widevariety of advanced communication features, including, but not limitedto, eMBB, uRLLC, and/or mMTC.

FIG. 2A is a schematic diagram of one example of a communication linkusing carrier aggregation. Carrier aggregation can be used to widenbandwidth of the communication link by supporting communications overmultiple frequency carriers, thereby increasing user data rates andenhancing network capacity by utilizing fragmented spectrum allocations.

In the illustrated example, the communication link is provided between abase station 21 and a mobile device 22. As shown in FIG. 2A, thecommunications link includes a downlink channel used for RFcommunications from the base station 21 to the mobile device 22, and anuplink channel used for RF communications from the mobile device 22 tothe base station 21.

Although FIG. 2A illustrates carrier aggregation in the context of FDDcommunications, carrier aggregation can also be used for TDDcommunications.

In certain implementations, a communication link can provideasymmetrical data rates for a downlink channel and an uplink channel.For example, a communication link can be used to support a relativelyhigh downlink data rate to enable high speed streaming of multimediacontent to a mobile device, while providing a relatively slower datarate for uploading data from the mobile device to the cloud.

In the illustrated example, the base station 21 and the mobile device 22communicate via carrier aggregation, which can be used to selectivelyincrease bandwidth of the communication link. Carrier aggregationincludes contiguous aggregation, in which contiguous carriers within thesame operating frequency band are aggregated. Carrier aggregation canalso be non-contiguous, and can include carriers separated in frequencywithin a common band or in different bands.

In the example shown in FIG. 2A, the uplink channel includes threeaggregated component carriers f_(UL1), f_(UL2), and f_(UL3).Additionally, the downlink channel includes five aggregated componentcarriers f_(DL1), f_(DL2), f_(DL3), f_(DL4), and f_(DL5). Although oneexample of component carrier aggregation is shown, more or fewercarriers can be aggregated for uplink and/or downlink. Moreover, anumber of aggregated carriers can be varied over time to achieve desireduplink and downlink data rates.

For example, a number of aggregated carriers for uplink and/or downlinkcommunications with respect to a particular mobile device can changeover time. For example, the number of aggregated carriers can change asthe device moves through the communication network and/or as networkusage changes over time.

FIG. 2B illustrates various examples of carrier aggregation for thecommunication link of FIG. 2A. FIG. 2B includes a first carrieraggregation scenario 31, a second carrier aggregation scenario 32, and athird carrier aggregation scenario 33, which schematically depict threetypes of carrier aggregation.

The carrier aggregation scenarios 31-33 illustrate different spectrumallocations for a first component carrier f_(cc1), a second componentcarrier f_(cc2), and a third component carrier f_(cc3). Although FIG. 2Bis illustrated in the context of aggregating three component carriers,carrier aggregation can be used to aggregate more or fewer carriers.

The first carrier aggregation scenario 31 illustrates intra-bandcontiguous carrier aggregation, in which component carriers that areadjacent in frequency and in a common frequency band are aggregated. Forexample, the first carrier aggregation scenario 31 depicts aggregationof component carriers f_(cc1), f_(cc2), and f_(cc3) that are contiguousand located within a first frequency band BAND1.

With continuing reference to FIG. 2B, the second carrier aggregationscenario 32 illustrates intra-band non-continuous carrier aggregation,in which two or more components carriers that are non-adjacent infrequency and within a common frequency band are aggregated. Forexample, the second carrier aggregation scenario 32 depicts aggregationof component carriers f_(cc1), f_(cc2), and f_(cc3) that arenon-contiguous, but located within a first frequency band BAND1.

The third carrier aggregation scenario 33 illustrates inter-bandnon-contiguous carrier aggregation, in which component carriers that arenon-adjacent in frequency and in multiple frequency bands areaggregated. For example, the third carrier aggregation scenario 33depicts aggregation of component carriers f_(cc1) and f_(cc2) of a firstfrequency band BAND1 with component carrier f_(cc3) of a secondfrequency band BAND2.

With reference to FIGS. 2A and 2B, the individual component carriersused in carrier aggregation can be of a variety of frequencies,including, for example, frequency carriers in the same band or inmultiple bands. Additionally, carrier aggregation is applicable toimplementations in which the individual component carriers are of aboutthe same bandwidth as well as to implementations in which the individualcomponent carriers have different bandwidths.

Certain communication networks allocate a particular user device with aprimary component carrier (PCC) or anchor carrier for uplink and a PCCfor downlink. Additionally, when the mobile device communicates using asingle frequency carrier for uplink or downlink, the user devicecommunicates using the PCC. To enhance bandwidth for uplinkcommunications, the uplink PCC can be aggregated with one or more uplinksecondary component carriers (SCCs). Additionally, to enhance bandwidthfor downlink communications, the downlink PCC can be aggregated with oneor more downlink SCCs.

In certain implementations, a communication network provides a networkcell for each component carrier. Additionally, a primary cell canoperate using a PCC, while a secondary cell can operate using a SCC. Theprimary and second cells may have different coverage areas, forinstance, due to differences in frequencies of carriers and/or networkenvironment.

License assisted access (LAA) refers to downlink carrier aggregation inwhich a licensed frequency carrier associated with a mobile operator isaggregated with a frequency carrier in unlicensed spectrum, such asWi-Fi. LAA employs a downlink PCC in the licensed spectrum that carriescontrol and signaling information associated with the communicationlink, while unlicensed spectrum is aggregated for wider downlinkbandwidth when available. LAA can operate with dynamic adjustment ofsecondary carriers to avoid Wi-Fi users and/or to coexist with Wi-Fiusers. Enhanced license assisted access (eLAA) refers to an evolution ofLAA that aggregates licensed and unlicensed spectrum for both downlinkand uplink.

FIG. 3A is a schematic diagram of one example of a downlink channelusing multi-input and multi-output (MIMO) communications. FIG. 3B isschematic diagram of one example of an uplink channel using MIMOcommunications.

MIMO communications use multiple antennas for simultaneouslycommunicating multiple data streams over common frequency spectrum. Incertain implementations, the data streams operate with differentreference signals to enhance data reception at the receiver. MIMOcommunications benefit from higher SNR, improved coding, and/or reducedsignal interference due to spatial multiplexing differences of the radioenvironment.

MIMO order refers to a number of separate data streams sent or received.For instance, MIMO order for downlink communications can be described bya number of transmit antennas of a base station and a number of receiveantennas for UE, such as a mobile device. For example, two-by-two (2×2)DL MIMO refers to MIMO downlink communications using two base stationantennas and two UE antennas. Additionally, four-by-four (4×4) DL MIMOrefers to MIMO downlink communications using four base station antennasand four UE antennas.

In the example shown in FIG. 3A, downlink MIMO communications areprovided by transmitting using M antennas 43 a, 43 b, 43 c, . . . 43 mof the base station 41 and receiving using N antennas 44 a, 44 b, 44 c,. . . 44 n of the mobile device 42. Accordingly, FIG. 3A illustrates anexample of M×N DL MIMO.

Likewise, MIMO order for uplink communications can be described by anumber of transmit antennas of UE, such as a mobile device, and a numberof receive antennas of a base station. For example, 2×2 UL MIMO refersto MIMO uplink communications using two UE antennas and two base stationantennas. Additionally, 4×4 UL MIMO refers to MIMO uplink communicationsusing four UE antennas and four base station antennas.

In the example shown in FIG. 3B, uplink MIMO communications are providedby transmitting using N antennas 44 a, 44 b, 44 c, . . . 44 n of themobile device 42 and receiving using M antennas 43 a, 43 b, 43 c, . . .43 m of the base station 41. Accordingly, FIG. 3B illustrates an exampleof N×M UL MIMO.

By increasing the level or order of MIMO, bandwidth of an uplink channeland/or a downlink channel can be increased.

MIMO communications are applicable to communication links of a varietyof types, such as FDD communication links and TDD communication links.

FIG. 4A is a schematic diagram of one example of a communication system110 that operates with beamforming. The communication system 110includes a transceiver 105, signal conditioning circuits 104 a 1, 104 a2 . . . 104 an, 104 b 1, 104 b 2 . . . 104 bn, 104 m 1, 104 m 2 . . .104 mn, and an antenna array 102 that includes antenna elements 103 a 1,103 a 2 . . . 103 an, 103 b 1, 103 b 2 . . . 103 bn, 103 m 1, 103 m 2 .. . 103 mn.

Communications systems that communicate using millimeter wave carriers(for instance, 30 GHz to 300 GHz), centimeter wave carriers (forinstance, 3 GHz to 30 GHz), and/or other frequency carriers can employan antenna array to provide beam formation and directivity fortransmission and/or reception of signals.

For example, in the illustrated embodiment, the communication system 110includes an array 102 of m×n antenna elements, which are each controlledby a separate signal conditioning circuit, in this embodiment. Asindicated by the ellipses, the communication system 110 can beimplemented with any suitable number of antenna elements and signalconditioning circuits.

With respect to signal transmission, the signal conditioning circuitscan provide transmit signals to the antenna array 102 such that signalsradiated from the antenna elements combine using constructive anddestructive interference to generate an aggregate transmit signalexhibiting beam-like qualities with more signal strength propagating ina given direction away from the antenna array 102.

In the context of signal reception, the signal conditioning circuitsprocess the received signals (for instance, by separately controllingreceived signal phases) such that more signal energy is received whenthe signal is arriving at the antenna array 102 from a particulardirection. Accordingly, the communication system 110 also providesdirectivity for reception of signals.

The relative concentration of signal energy into a transmit beam or areceive beam can be enhanced by increasing the size of the array. Forexample, with more signal energy focused into a transmit beam, thesignal is able to propagate for a longer range while providingsufficient signal level for RF communications. For instance, a signalwith a large proportion of signal energy focused into the transmit beamcan exhibit high effective isotropic radiated power (EIRP).

In the illustrated embodiment, the transceiver 105 provides transmitsignals to the signal conditioning circuits and processes signalsreceived from the signal conditioning circuits. As shown in FIG. 4A, thetransceiver 105 generates control signals for the signal conditioningcircuits. The control signals can be used for a variety of functions,such as controlling the phase of transmitted or received signals tocontrol beam forming.

FIG. 4B is a schematic diagram of one example of beamforming to providea transmit beam. FIG. 4B illustrates a portion of a communication systemincluding a first signal conditioning circuit 114 a, a second signalconditioning circuit 114 b, a first antenna element 113 a, and a secondantenna element 113 b.

Although illustrated as included two antenna elements and two signalconditioning circuits, a communication system can include additionalantenna elements and/or signal conditioning circuits. For example, FIG.4B illustrates one embodiment of a portion of the communication system110 of FIG. 4A.

The first signal conditioning circuit 114 a includes a first phaseshifter 130 a, a first power amplifier 131 a, a first low noiseamplifier (LNA) 132 a, and switches for controlling selection of thepower amplifier 131 a or LNA 132 a. Additionally, the second signalconditioning circuit 114 b includes a second phase shifter 130 b, asecond power amplifier 131 b, a second LNA 132 b, and switches forcontrolling selection of the power amplifier 131 b or LNA 132 b.

Although one embodiment of signal conditioning circuits is shown, otherimplementations of signal conditioning circuits are possible. Forinstance, in one example, a signal conditioning circuit includes one ormore band filters, duplexers, and/or other components.

In the illustrated embodiment, the first antenna element 113 a and thesecond antenna element 113 b are separated by a distance d.Additionally, FIG. 4B has been annotated with an angle θ, which in thisexample has a value of about 90° when the transmit beam direction issubstantially perpendicular to a plane of the antenna array and a valueof about 0° when the transmit beam direction is substantially parallelto the plane of the antenna array.

By controlling the relative phase of the transmit signals provided tothe antenna elements 113 a, 113 b, a desired transmit beam angle θ canbe achieved. For example, when the first phase shifter 130 a has areference value of 0°, the second phase shifter 130 b can be controlledto provide a phase shift of about −2πf(d/ν)cos θ radians, where f is thefundamental frequency of the transmit signal, d is the distance betweenthe antenna elements, ν is the velocity of the radiated wave, and π isthe mathematic constant pi.

In certain implementations, the distance d is implemented to be about½λ, where λ is the wavelength of the fundamental component of thetransmit signal. In such implementations, the second phase shifter 130 bcan be controlled to provide a phase shift of about −π cos θ radians toachieve a transmit beam angle θ.

Accordingly, the relative phase of the phase shifters 130 a, 130 b canbe controlled to provide transmit beamforming. In certainimplementations, a transceiver (for example, the transceiver 105 of FIG.4A) controls phase values of one or more phase shifters to controlbeamforming.

FIG. 4C is a schematic diagram of one example of beamforming to providea receive beam. FIG. 4C is similar to FIG. 4B, except that FIG. 4Cillustrates beamforming in the context of a receive beam rather than atransmit beam.

As shown in FIG. 4C, a relative phase difference between the first phaseshifter 130 a and the second phase shifter 130 b can be selected toabout equal to −2πf(d/ν)cos θ radians to achieve a desired receive beamangle θ. In implementations in which the distance d corresponds to about½λ, the phase difference can be selected to about equal to −π cos θradians to achieve a receive beam angle θ.

Although various equations for phase values to provide beamforming havebeen provided, other phase selection values are possible, such as phasevalues selected based on implementation of an antenna array,implementation of signal conditioning circuits, and/or a radioenvironment.

Cascode Power Amplifiers with Separated Cascode Biasing for OscillationSuppression

A cascode power amplifier includes a transconductance device, such as acommon emitter transistor or a common source transistor, connected inseries with a cascode device, such as a common base transistor or acommon gate transistor. A cascode power amplifier can exhibit high gain,wide bandwidth, superior impedance characteristics, and/or a number ofother desirable performance parameters.

To achieve a certain output power handling capability, a cascode poweramplifier can be implemented using multiple transistor cells that areelectrically connected in parallel with one another. By parallelizingtransistor cells, the cascode power amplifier's power handlingcapability can be scaled to achieve a desired power performance.

The inventor has recognized that oscillation can arise in a cascodepower amplifier when a common or shared bias is used to bias the cascodedevices of multiple transistor cells of the cascode power amplifier. Inparticular, a cascode power amplifier using a common bias for eachcascode device can behave at high frequencies as a differential Colpittsoscillator.

For example, a shared bias voltage can be routed using a metal conductorto the gate or base of each cascode device, and an AC groundingcapacitor can be provided for each cascode device between the gate orbase and ground. Although the AC grounding capacitors theoreticallyprovide AC ground to the cascode devices, the inventor has recognizedthat a parasitic inductance is present between each AC groundingcapacitor and ground. Additionally, the parasitic inductance and ACgrounding capacitor resonate at a resonant frequency, above which theseries combination of the AC grounding capacitor and parasiticinductance behaves inductively. The metal conductor used for biasingalso exhibits parasitic inductance, and thus at high frequenciesinductance is present between the cascode devices. The combination ofthe parasitic inductances and transistor junction capacitances result inthe cascode power amplifier behaving as a differential Colpittsoscillator at high frequencies.

Although a relatively short biasing conductor having low inductance canbe used to distribute a shared bias signal to the cascode devices, thecascode power amplifier's layout can be constrained by a limitation onthe biasing conductor's length. Moreover, when providing amplificationto RF signals of relatively high frequency, for instance, 5 GHz or more,a cascode power amplifier can be susceptible to oscillation in thepresence of even relatively small parasitic inductances and shortconductor lengths.

Apparatus and methods for oscillation suppression of cascode poweramplifiers are provided herein. In certain implementations, a poweramplifier system includes a cascode power amplifier including aplurality of transconductance devices that operate in combination with aplurality of cascode devices to amplify a radio frequency input signal.The power amplifier system further includes a bias circuit that biasesthe plurality of cascode devices with two or more bias voltages that aredecoupled from one another at radio frequency.

By implementing the cascode power amplifier in this manner, the cascodepower amplifier exhibits enhanced robustness against oscillation.Furthermore, the cascode power amplifier can be implemented with relaxedlayout constraints, such as distance between the transistor cells,without inadvertently oscillating.

The cascode power amplifiers herein can be used to amplify a wide rangeof frequencies, including relatively high radio frequencies of 5 GHz ormore, for instance, millimeter wave frequencies in the range of about 30GHz to about 300 GHz. In certain implementations, the two or more biasvoltages used for biasing are substantially decoupled from one anotherat frequencies greater than 450 megahertz (MHz).

The cascode power amplifier biasing schemes disclosed herein areapplicable to a wide variety of RF communication systems, including, butnot limited to, smartphones, base stations, laptops, handsets, wearableelectronics, and/or tablets.

FIG. 5 is a schematic diagram of one embodiment of a power amplifiersystem 210 with separated cascode biasing. The power amplifier system210 includes an input terminal RF_(IN), an output terminal RF_(OUT), abias circuit 204, a choke inductor 205, and a cascode power amplifier206 that includes transconductance (g_(m)) devices 201 a-201 c andcascode devices 202 a-202 c.

In the illustrated embodiment, the cascode power amplifier 206 includesmultiple transistor cells that are electrically connected in parallelwith one another. Additionally, each transistor cell includes atransconductance device and cascode device that is electricallyconnected in series with one another. For example, the cascode poweramplifier 206 includes a first transistor cell associated with the firsttransconductance device 201 a and the first cascode device 202 a, asecond transistor cell associated with the second transconductancedevice 201 b and the second cascode device 202 b, and a third transistorcell associated with the third transconductance device 201 c and thethird cascode device 202 c.

By parallelizing transistor cells, the cascode power amplifier's powerhandling capability can be increased to achieve a desired output powerhandling capability. Although an implementation with three transistorcells is shown in FIG. 5, a cascode power amplifier can include more orfewer transistor cells connected in parallel, as indicated by theellipses. In one implementation, the cascode power amplifier 206includes at least four transistor cells. In another implementation, thecascode power amplifier 206 includes at least eight transistor cells.

During operation of the power amplifier system 210, the input terminalRF_(IN) receives an RF input signal, and the output terminal RF_(OUT)provides an RF output signal. Additionally, the transconductance devices201 a-201 c operate in combination with the cascode devices 202 a-202 cto amplify the RF input signal to generate the RF output signal.

The illustrated power amplifier system 210 further includes the chokeinductor 205, which is electrically connected between the supply voltageSUP and the output terminal RF_(OUT). The choke inductor 205 serves toprovide the supply voltage SUP to the cascode devices 202 a-202 c, whilechoking or blocking the RF output signal.

As shown in FIG. 5, the bias circuit 204 biases the cascode devices 202a-202 c with bias signals that are decoupled from one another at radiofrequency to provide oscillation suppression to the power amplifiersystem 210. In the illustrated embodiment, each of the cascode devices202 a-202 c receives a separate bias signal. Thus, the bias signals aredisconnected from one another, in this embodiment.

The inventor has recognized that oscillation can arise in a cascodepower amplifier when a common or shared bias is used to bias the cascodedevices of multiple transistor cells of a cascode power amplifier. Inparticular, a cascode power amplifier including multiple transistorcells biased using a common bias can behave at high frequencies as adifferential Colpitts oscillator. Although a relatively short biasingconductor can be used to provide the bias voltage to the cascodedevices, such a short biasing conductor can constrain the cascode poweramplifier's layout. Oscillation of cascode power amplifiers using ashared bias can be particular exacerbated in high frequencyapplications, for instance, 5 GHz or more, in which such a cascode poweramplifier can be susceptible to oscillation in the presence of evenrelatively small parasitic inductances and short wire lengths.

In contrast, the illustrated power amplifier system 210 is implementedwith the bias circuit 204, which biases the cascode devices 202 a-202 cwith separate bias signals. Accordingly, the power amplifier system 210can exhibit robustness against unintended oscillations. Furthermore, thecascode power amplifier 206 can be implemented with relaxed layoutconstraints, such as distance between the transistor cells, withoutinadvertently oscillating.

FIG. 6 is a schematic diagram of one embodiment of an RF communicationsystem 230. The illustrated RF communication system 230 includes a chokeinductor 205, a cascode power amplifier 212, a bias circuit 214, asupply control circuit 215, switches 216, an antenna 217, a directionalcoupler 218, and a transmitter 219. The transmitter 219 can be includedin a transceiver that also includes circuitry associated with receivingsignals from an antenna (for instance, via the antenna 217 or a separateantenna) over one or more receive paths.

The cascode power amplifier 212 includes transconductance devices 227(implemented as common emitter bipolar transistors, in this embodiment)and cascode devices 228 (implemented as common base bipolar transistors,in this embodiment). Although the RF communication system 230 of FIG. 6illustrates one example of an RF communication system that can include acascode power amplifier, the teachings herein are applicable to RFcommunication systems implemented in a wide variety of ways.

Although the illustrated cascode power amplifier 212 is illustrated as asingle stage, the teachings herein are also applicable to multi-stageconfigurations including two or more stages. In certain implementations,a cascode output stage of a multi-stage power amplifier includes thetransconductance devices 227 and the cascode devices 228. In certainembodiments, two or more cascode devices are included in series witheach transconductance device. Thus, a cascode amplifier can beimplemented with transistor cells including a stack of three or moretransistors. In such implementations, all or part of the cascode devices(for instance, upper cascode transistors and/or lower cascodetransistors) can include separated cascode biasing.

In the illustrated embodiment, the cascode power amplifier 212 amplifiesan RF input signal received from the I/Q modulator 222 of thetransmitter 219. The amplified RF signal generated by the cascode poweramplifier 212 can be provided to the antenna 217 by way of the switches216.

As shown in FIG. 6, the cascode power amplifier 212 receives a supplyvoltage SUP from the supply control circuit 215.

In certain implementations, the supply control circuit 215 dynamicallychanges the voltage level of the supply voltage SUP over time, forinstance, using one or more DC-to-DC converters and/or error amplifiers.For example, the supply control circuit 215 can be implemented toprovide average power tracking (APT), envelope tracking (ET), and/or anyother suitable supply control scheme. In other implementations, thesupply voltage SUP is substantially fixed.

The bias signals received by the cascode power amplifier 212 from thebias circuit 214 bias the cascode power amplifier 212. As shown in FIG.6, the bias circuit 214 provides the cascode devices 228 with separatebias signals to enhance the robustness of the cascode power amplifier212 against oscillations.

In the illustrated embodiment, the bias circuit 214 also provides thetransconductance devices 227 with a common bias signal. However, otherconfigurations are possible, for instance, implementations in which thetransconductance devices are separately biased.

In the illustrated RF communication system 230, the directional coupler218 is positioned between the output of the cascode power amplifier 212and the input of the switches 216, thereby allowing a measurement ofoutput power of the cascode power amplifier 212 that does not includeinsertion loss of the switches 216. The sensed output signal from thedirectional coupler 218 can be provided to the mixer 223, which canmultiply the sensed output signal by a reference signal of a controlledfrequency so as to downshift the frequency content of the sensed outputsignal to generate a downshifted signal. The downshifted signal can beprovided to the ADC 224, which can convert the downshifted signal to adigital format suitable for processing by the baseband processor 221.

By including a feedback path between the output of the cascode poweramplifier 212 and the baseband processor 221, the baseband processor 221can be configured to dynamically adjust the I and Q signals to optimizethe operation of the RF communication system 230. For example,configuring the RF communication system 230 in this manner can aid incontrolling the power added efficiency (PAE) and/or linearity of thecascode power amplifier 212.

The baseband signal processor 221 can generate an I signal and a Qsignal, which can be used to represent a sinusoidal wave or signal of adesired amplitude, frequency, and phase. For example, the I signal canbe used to represent an in-phase component of the sinusoidal wave andthe Q signal can be used to represent a quadrature component of thesinusoidal wave, which can be an equivalent representation of thesinusoidal wave. In certain implementations, the I and Q signals can beprovided to the I/Q modulator 222 in a digital format. The basebandprocessor 221 can be any suitable processor configured to process abaseband signal. For instance, the baseband processor 221 can include adigital signal processor, a microprocessor, a programmable core, or anycombination thereof. Moreover, in some implementations, two or morebaseband processors 221 can be included in the RF communication system230.

The I/Q modulator 222 can receive the I and Q signals from the basebandprocessor 221 and to process the I and Q signals to generate an RFsignal. For example, the I/Q modulator 222 can include digital-to-analogconverters (DACs) configured to convert the I and Q signals into ananalog format, mixers for upconverting the I and Q signals to radiofrequency, and a signal combiner for combining the upconverted I and Qsignals into an RF signal suitable for amplification by the cascodepower amplifier 212. In certain implementations, the I/Q modulator 222can include one or more filters configured to filter frequency contentof signals processed therein.

FIG. 7A is a schematic diagram of another embodiment of a poweramplifier system 250 with separated cascode biasing. The power amplifiersystem 250 includes an input terminal RF_(IN), an output terminalRF_(OUT), a bias circuit 204, a choke inductor 205, and a cascode poweramplifier 256 that includes common emitter bipolar transistors 251 a-251c, common base bipolar transistors 252 a-252 c, and degenerationresistors 203 a-203 c.

The power amplifier system 250 of FIG. 7A is similar to the poweramplifier system 210 of FIG. 5, except that the power amplifier system250 illustrates a specific implementation of transconductance andcascode devices, and illustrates an implementation includingdegeneration circuitry.

For example, the power amplifier system 250 of FIG. 7A includestransconductance devices implemented as common emitter bipolartransistors 251 a-251 c and cascode devices implemented as common basebipolar transistors 252 a-252 c. Additionally, the power amplifiersystem 250 includes degeneration circuits, implemented as degenerationresistors 203 a-203 c, in this embodiment. In another embodiment, thedegeneration circuitry includes degeneration inductors or a combinationof degeneration resistors and degeneration inductors.

Although one example of a cascode power amplifier with separate cascodebiasing is shown, the teachings herein are applicable to cascode poweramplifiers implemented in a wide variety of ways.

FIG. 7B is a schematic diagram of another embodiment of a poweramplifier system 260 with separated cascode biasing. The power amplifiersystem 260 includes an input terminal RF_(IN), an output terminalRF_(OUT), a bias circuit 204, a choke inductor 205, and a cascode poweramplifier 266 that includes common source field-effect transistors 261a-261 c (FETs), common gate FETs 262 a-262 c, and degeneration resistors203 a-203 c.

The power amplifier system 260 of FIG. 7B is similar to the poweramplifier system 250 of FIG. 7A, except that the power amplifier system260 is implemented using FETs rather than bipolar transistors. Forexample, the power amplifier system 260 of FIG. 7B includestransconductance devices implemented as common source FETs 261 a-261 cand cascode devices implemented as common gate FETs 262 a-262 c.

FIG. 7C is a schematic diagram of another embodiment of a poweramplifier system 270 with separated cascode biasing. The power amplifiersystem 270 includes an input terminal RF_(IN), an output terminalRF_(OUT), a bias circuit 204, a choke inductor 205, and a cascode poweramplifier 276 that includes common source FETs 261 a-261 c, common basebipolar transistors 252 a-252 c, and degeneration resistors 203 a-203 c.

The power amplifier system 270 illustrates one example of a cascodepower amplifier that includes a combination of bipolar transistors andfield-effect transistors. However, other implementations of cascodepower amplifiers using a combination of transistor types are possible.

FIG. 7D is a schematic diagram of another embodiment of a poweramplifier system 280 with separated cascode biasing. The power amplifiersystem 280 includes an input terminal RF_(IN), an output terminalRF_(OUT), a bias circuit 204, a choke inductor 205, and a cascode poweramplifier 286 that includes common emitter bipolar transistors 251 a-251c, common gate FETs 262 a-262 c, and degeneration resistors 203 a-203 c.

The power amplifier system 280 illustrates another example of a cascodepower amplifier that includes a combination of bipolar and FETs. Thepower amplifier system 280 also illustrates an embodiment in which anintermediate connection between each pair of transconductance andcascode devices is connected at a shared or common node. Any of thecascode power amplifiers described herein can be modified to includesuch an intermediate connection between transconductance devices andcascode devices.

The cascode power amplifier 280 of FIG. 7D illustrates another exampleof a cascode power amplifier with separate cascode biasing. However, theteachings herein are applicable to cascode power amplifiers implementedin a wide variety of ways.

FIG. 8A is a schematic diagram of another embodiment of a poweramplifier system 310 with separated cascode biasing. The power amplifiersystem 310 includes an input terminal RF_(IN), an output terminalRF_(OUT), a bias circuit 304, a choke inductor 205, and a cascode poweramplifier 316 that includes common emitter bipolar transistors 301 a-301h, common base bipolar transistors 302 a-302 h, degeneration resistors303 a-303 h, and through-wafer vias (TWVs) 305 a-305 d.

As persons of ordinary skill in the art will appreciate, a semiconductordie includes a first or active side including semiconductor devicesfabricated thereon, and a second or back side opposite to the activeside. Additionally, a TWV provides an electrical connection through thedie from the active side to the back side. For example, one or more TWVscan be included on the die to provide an electrical connection betweencircuitry fabricated on the active side and a backside conductorcarrying a ground voltage.

In the illustrated embodiment, eight transistor cells have beenelectrically connected in parallel. By parallelizing transistor cells,the cascode power amplifier's power handling capability can be increasedto achieve a desired output power handling capability. Although animplementation with eight transistor cells is shown in FIG. 8A, acascode power amplifier can include more or fewer transistor cellsconnected in parallel.

As shown in FIG. 8A, the illustrated common base bipolar transistors 302a-302 h each include a base that is provided with a separate biasvoltage. In particular, common base bipolar transistors 302 a-302 hreceive bias voltages V_(BIAS1), V_(BIAS2), V_(BIAS3), V_(BIAS4),V_(BIAS5), V_(BIAS6), V_(BIAS7), and V_(BIAS8), respectively. Byimplementing the cascode power amplifier in this manner, inductance iseliminated between the bases of the common base bipolar transistors 302a-302 h.

In contrast, a cascode power amplifier with a shared bias circuit canhave inductance present between the cascode devices, which can lead tothe cascode power amplifier operating as an oscillator at highfrequencies.

Although certain layout techniques, such as a short common biasconductor can reduce an amount of parasitic inductance between cascodedevices, layout techniques alone may be insufficient to suppressoscillations. For instance, a cascode power amplifier that providesamplification to relatively high frequencies, such as millimeter wavefrequencies, may be susceptible to oscillation when even a relativelysmall amount of inductance is present between the cascode poweramplifier's cascode devices. Accordingly, such a cascode power amplifiermay oscillate in high frequency applications even when using a commonbias implemented using a relatively short biasing conductor.

FIG. 8B is a schematic diagram of another embodiment of a poweramplifier system 320 with separated cascode biasing. The power amplifiersystem 320 includes an input terminal RF_(IN), an output terminalRF_(OUT), a bias circuit 314, a choke inductor 205, and a cascode poweramplifier 326 that includes common emitter bipolar transistors 301 a-301h, common base bipolar transistors 302 a-302 h, degeneration resistors303 a-303 h, and TWVs 305 a-305 d.

The power amplifier system 320 of FIG. 8B is similar to the poweramplifier system 310 of FIG. 8A, except that the power amplifier system320 of FIG. 8B illustrates an implementation in which four bias voltagesare used to bias eight common base cascode transistors.

For example, in the illustrated embodiment, common base bipolartransistors 302 a-302 b receive V_(BIAS1)′, common base bipolartransistors 302 c-302 d receive V_(BIAS2)′, common base bipolartransistors 302 e-302 f receive V_(BIAS3)′, and common base bipolartransistors 302 g-302 h receive V_(BIAS4)′.

In certain embodiments, multiple bias signals (for instance, biasvoltages) are used to bias multiple cascode devices. However, certaincascode devices, such as cascode devices that are in close physicalproximity to one another on chip, can operate using a shared bias.

FIG. 8C is a schematic diagram of another embodiment of a poweramplifier system 350 with separated cascode biasing. The power amplifiersystem 350 includes an input terminal RF_(IN), an output terminalRF_(OUT), a bias circuit 304, a choke inductor 205, and a cascode poweramplifier 356 that includes common emitter bipolar transistors 301 a-301h, common base bipolar transistors 302 a-302 h, degeneration resistors303 a-303 h, TWVs 305 a-305 d, and RF isolation circuits 331 a-331 g.

The power amplifier system 350 of FIG. 8C is similar to the poweramplifier system 310 of FIG. 8A, except that the power amplifier system350 of FIG. 8C includes the RF isolation circuits 331 a-331 g.

The RF isolation circuits 331 a-331 g are used to provide RF isolationbetween cascode devices (thus substantially blocking RF signals), whileproviding DC coupling to aid in reducing or eliminating variation in theDC bias voltage levels of the bias voltages generated by the biascircuit 304.

Although FIG. 8C illustrates an example in which RF isolation circuits(for instance, inductors and/or resistors) are used to provide RFisolation, in other embodiments electrically disconnected conductors areused to bias different cascode devices. Such electrically disconnectedconductors can include a first biasing conductor separated from a secondbiasing conductor by dielectric, thereby isolating the first biasingconductor and the second biasing conductor from one another. Suchbiasing conductors can further include shielding to inhibitelectromagnetic fields from impacting the voltages of the biasingconductors.

FIG. 9 is a schematic diagram of another embodiment of a power amplifiersystem 370 with separated cascode biasing. The power amplifier system370 includes an input terminal RF_(IN), an output terminal RF_(OUT), abias circuit 360, a choke inductor 205, and a cascode power amplifierthat includes common emitter bipolar transistors 301 a-301 b, commonbase bipolar transistors 302 a-302 b, degeneration resistors 303 a-303b, and a TWV 305.

The power amplifier system 370 of FIG. 9 illustrates one embodiment of abias circuit 360 for a cascode power amplifier. The illustrated biascircuit 360 includes emitter follower bipolar transistors 351 a-351 b,AC grounding capacitors 352 a-352 b, biasing resistors 307 a-307 b, andTWVs 306 a-306 c. Although one embodiment of a bias circuit for acascode power amplifier is shown, the teachings herein are applicable tobias circuits implemented in a wide variety of ways.

The illustrated bias circuit 360 includes a first follower transistor(implemented as emitter follower bipolar transistor 351 a, in thisembodiment) that generates a first bias voltage and a second followertransistor (implemented as a second emitter follower bipolar transistor351 b, in this embodiment) that generates a second bias voltage.Follower transistors (for instance, emitter follower bipolar transistorsand/or source follower FETs) are used to generate separate biasvoltages, in certain embodiments.

Additionally, an AC grounding capacitor is included between the base ofeach cascode device and ground. For example, the AC grounding capacitor352 a is electrically connected between the base of the common basebipolar transistor 302 a and ground, and the AC grounding capacitor 352b is electrically connected between the base of the common base bipolartransistor 302 b and ground. In the illustrated embodiment, the ACgrounding capacitors are electrically connected to ground by way of TWVs306 a-306 b, respectively.

The follower transistors 351 a-351 b receive a common reference voltage,in this embodiment. In the illustrated embodiment, the common referencevoltage is generated by a voltage divider, which is implemented usingresistors 307 a-307 b electrically connected in series with the TWV 306c, in this embodiment. The voltage divider is connected between thesupply voltage SUP and ground, in this embodiment.

FIG. 10A is a schematic diagram of one example of a power amplifiersystem with shared cascode biasing. The power amplifier system includestwo transistor cells electrically connected in parallel and biased usinga common bias voltage.

With continuing reference to FIG. 10A, Q_(1A) is a common emittertransistor of a left power cell, Q_(2A) is a common base transistor ofthe left power cell, and R1 is a degeneration resistor of the left powercell. Additionally, Q_(1B) is a common emitter transistor of a rightpower cell, Q_(2B) is a common base transistor of the right power cell,and R2 is a degeneration resistor of the right power cell. Furthermore,L_(WIRE) represents a parasitic inductance of the shared base biasingwire. Additionally, C_(dA) and C_(dB) are explicit AC groundingcapacitors to AC ground the base nodes of the common base transistors.Furthermore, L_(TWV) represents the inductance of the through wafer vias(TWVs) used to ground the bottom plate of the AC grounding capacitors.Additionally, C_(π2A), C_(π2B), C_(μ2A), and C_(μ2B) represent junctioncapacitances present in the transistors.

Ideally, C_(dA) and C_(dB) provide a short circuit to ground the basesof both Q2A and Q2B. However, due to the inductance of the TWVs, at somefrequency these capacitors resonate with the TWV inductance and abovethis frequency this path behaves inductively and forms a second inductorin parallel with L_(WIRE).

FIG. 10B is a schematic diagram representing high frequency operation ofthe power amplifier system of FIG. 10A.

FIG. 10C is a schematic diagram of one example of a differentialColpitts oscillator. The differential Colpitts oscillator includes afirst bipolar transistor Q1, a second bipolar transistor Q2, a firstbase-to-emitter capacitor C_(1A), a second base-to-emitter capacitorC_(1B), a capacitor C2, an inductor L, a first bias current sourceI_(BIAS1), and a second bias current source I_(BIAS2).

As shown by a comparison of FIGS. 10B and 10C, at high frequencies thepower amplifier system of FIG. 10A can behave as a differential Colpittsoscillator.

Examples of Electronic Systems Including Cascode Power Amplifiers

A cascode power amplifier can be integrated on a semiconductor die,which in turn can be included in a wide variety of electronic systems.

FIG. 11A is a schematic diagram of a front end system 630 according toone embodiment. FIG. 11B is a schematic diagram of a front end system640 according to another embodiment.

An RF front end system can include circuits in a signal path between anantenna and a baseband system. Some RF front ends can include circuitsin signal paths between one or more antennas and a mixer configured tomodulate a signal to RF or to demodulate an RF signal.

The front end systems of FIGS. 11A and 11B can be implemented in apackaged module. Such packaged modules can include relatively low costlaminate based front end modules that combine power amplifiers with lownoise amplifiers and/or switch functions. Some such packaged modules canbe multi-chip modules. In certain implementations, some or the all ofthe illustrated components in any of the front end systems in FIGS. 11Aand/or 11B can be embodied on a single integrated circuit or die. Such adie can be manufactured using any suitable process technology. Accordingto some implementations, one or more antennas can be integrated with anyof the front end systems discussed herein.

With reference to FIG. 11A, the RF front end system 630 is configured toreceive RF signals from an antenna 641 and to transmit RF signals by wayof the antenna 641. The illustrated front end system 630 includes afirst multi-throw switch 642, a second multi-throw switch 643, a receivesignal path that includes an LNA 646, a bypass signal path that includesa bypass network 644, and a transmit signal path that includes a cascodepower amplifier 645. The low noise amplifier 646 can be implemented byany suitable low noise amplifier. The bypass network 644 can include anysuitable network for matching and/or bypassing the receive signal pathand the transmit signal path. The bypass network 644 can be implementedby a passive impedance network or by a conductive trace or wire.

The cascode power amplifier 645 can be implemented in accordance withany of the principles and advantages discussed herein. In theillustrated embodiment, the cascode power amplifier 645 is a multi-stagepower amplifier including at least an input stage and an output stage.In certain implementations, the output stage of the cascode poweramplifier 645 includes multiple transistor cells including cascodedevices that are separately biased by the control and biasing circuit647.

The first multi-throw switch 642 can selectively connect a particularsignal path to the antenna 641. The first multi-throw switch 642 canelectrically connect the transmit signal path to the antenna 641 in afirst state, electrically connect the receive signal path to the antenna641 in a second state, and electrically connect the bypass signal pathto the antenna 641 in a third state. The second multi-throw switch 643can selectively connect a particular signal path to an input/output portof the front end system 630, in which the particular signal path is thesame signal path electrically connected to the antenna 641 by way of thefirst multi-throw switch 642. Accordingly, the second multi-throw switch643 together with the first multi-throw switch 642 can selectivelyconnect a particular signal path between the antenna 641 and theinput/output port of the front end system 630.

The control and biasing circuit 647 can be used to control and biascircuitry of the RF front end system 630. In certain configurations, thecontrol and biasing circuit 647 receives a mode control signalindicating a mode of operation of the cascode power amplifier 645. Themode control signal can be provided to the control and biasing circuit647 in a variety of ways, such as over a serial interface. The controland biasing circuit 647 can use the mode control signal for a variety ofpurposes, including, for example, controlling a voltage level of asupply voltage used to power the cascode power amplifier 645 and/orcontrolling bias signal level of the cascode devices of the cascodepower amplifier 645.

The RF front end system 640 of FIG. 11B is similar to the RF front endsystem 630 of FIG. 11A, except that the first multi-throw switch 649 isconfigured to selectively connect a particular signal path to either afirst antenna 641 or a second antenna 648. The multi-throw switch 649can be a multi-throw, multi-pole switch.

FIG. 12A is a schematic diagram of a wireless communication device 650according to one embodiment. FIG. 12B is a schematic diagram of awireless communication device 660 according to another embodiment.

FIGS. 12A and 12B are schematic block diagrams of illustrative wirelesscommunication devices that include a cascode power amplifier inaccordance with one or more embodiments.

As illustrated, the wireless communication device 650 includes a firstantenna 641, a wireless personal area network (WPAN) system 651, atransceiver 652, a processor 653, a memory 654, a power management block655, a second antenna 656, and an RF front end system 657. Any of thecascode power amplifiers discussed herein can be implemented in the WPANsystem 651 and/or the RF front end system 657. The WPAN system 651 is anRF front end system configured for processing RF signals associated withpersonal area networks (PANs). The WPAN system 651 can be configured totransmit and receive signals associated with one or more WPANcommunication standards, such as signals associated with one or more ofBluetooth, ZigBee, Z-Wave, Wireless USB, INSTEON, IrDA, or Body AreaNetwork. In another embodiment, a wireless communication device caninclude a wireless local area network (WLAN) system in place of theillustrated WPAN system, and the WLAN system can process Wi-Fi signals.

The illustrated wireless communication device 660 of FIG. 12B is adevice configured to communicate over a PAN. This wireless communicationdevice can be relatively less complex than the wireless communicationdevice 650 of FIG. 12A. As illustrated, the wireless communicationdevice 660 includes an antenna 641, a WPAN system 651, a transceiver662, a processor 653, and a memory 654. The WPAN system 660 can includeone or more RF amplifiers in accordance with any of the principles andadvantages discussed herein.

FIG. 13 is a schematic diagram of one embodiment of a mobile device 800.The mobile device 800 includes a baseband system 801, a transceiver 802,a front end system 803, antennas 804, a power management system 805, amemory 806, a user interface 807, and a battery 808.

The mobile device 800 can be used communicate using a wide variety ofcommunications technologies, including, but not limited to, 2G, 3G, 4G(including LTE, LTE-Advanced, and LTE-Advanced Pro), 5G NR, WLAN (forinstance, Wi-Fi), WPAN (for instance, Bluetooth and ZigBee), WMAN (forinstance, WiMax), and/or GPS technologies.

The transceiver 802 generates RF signals for transmission and processesincoming RF signals received from the antennas 804. It will beunderstood that various functionalities associated with the transmissionand receiving of RF signals can be achieved by one or more componentsthat are collectively represented in FIG. 13 as the transceiver 802. Inone example, separate components (for instance, separate circuits ordies) can be provided for handling certain types of RF signals.

The front end system 803 aids is conditioning signals transmitted toand/or received from the antennas 804. In the illustrated embodiment,the front end system 803 includes power amplifiers (PAs) 811, low noiseamplifiers (LNAs) 812, filters 813, switches 814, and duplexers 815.However, other implementations are possible.

For example, the front end system 803 can provide a number offunctionalities, including, but not limited to, amplifying signals fortransmission, amplifying received signals, filtering signals, switchingbetween different bands, switching between different power modes,switching between transmission and receiving modes, duplexing ofsignals, multiplexing of signals (for instance, diplexing ortriplexing), or some combination thereof.

At least one of the power amplifiers 811 is a cascode power amplifierimplemented in accordance with one or more features disclosed herein.

In certain implementations, the mobile device 800 supports carrieraggregation, thereby providing flexibility to increase peak data rates.Carrier aggregation can be used for both Frequency Division Duplexing(FDD) and Time Division Duplexing (TDD), and may be used to aggregate aplurality of carriers or channels. Carrier aggregation includescontiguous aggregation, in which contiguous carriers within the sameoperating frequency band are aggregated. Carrier aggregation can also benon-contiguous, and can include carriers separated in frequency within acommon band or in different bands.

The antennas 804 can include antennas used for a wide variety of typesof communications. For example, the antennas 804 can include antennasfor transmitting and/or receiving signals associated with a wide varietyof frequencies and communications standards.

In certain implementations, the antennas 804 support MIMO communicationsand/or switched diversity communications. For example, MIMOcommunications use multiple antennas for communicating multiple datastreams over a single radio frequency channel. MIMO communicationsbenefit from higher signal to noise ratio, improved coding, and/orreduced signal interference due to spatial multiplexing differences ofthe radio environment. Switched diversity refers to communications inwhich a particular antenna is selected for operation at a particulartime. For example, a switch can be used to select a particular antennafrom a group of antennas based on a variety of factors, such as anobserved bit error rate and/or a signal strength indicator.

The mobile device 800 can operate with beamforming in certainimplementations. For example, the front end system 803 can include phaseshifters having variable phase controlled by the transceiver 802.Additionally, the phase shifters are controlled to provide beamformation and directivity for transmission and/or reception of signalsusing the antennas 804. For example, in the context of signaltransmission, the phases of the transmit signals provided to theantennas 804 are controlled such that radiated signals from the antennas804 combine using constructive and destructive interference to generatean aggregate transmit signal exhibiting beam-like qualities with moresignal strength propagating in a given direction. In the context ofsignal reception, the phases are controlled such that more signal energyis received when the signal is arriving to the antennas 804 from aparticular direction. In certain implementations, the antennas 804include one or more arrays of antenna elements to enhance beamforming.

The baseband system 801 is coupled to the user interface 807 tofacilitate processing of various user input and output (I/O), such asvoice and data. The baseband system 801 provides the transceiver 802with digital representations of transmit signals, which the transceiver802 processes to generate RF signals for transmission. The basebandsystem 801 also processes digital representations of received signalsprovided by the transceiver 802. As shown in FIG. 13, the basebandsystem 801 is coupled to the memory 806 of facilitate operation of themobile device 800.

The memory 806 can be used for a wide variety of purposes, such asstoring data and/or instructions to facilitate the operation of themobile device 800 and/or to provide storage of user information.

The power management system 805 provides a number of power managementfunctions of the mobile device 800. In certain implementations, thepower management system 805 includes a PA supply control circuit thatcontrols the supply voltages of the power amplifiers 811. For example,the power management system 805 can be configured to change the supplyvoltage(s) provided to one or more of the power amplifiers 811 toimprove efficiency, such as power added efficiency (PAE).

As shown in FIG. 13, the power management system 805 receives a batteryvoltage from the battery 808. The battery 808 can be any suitablebattery for use in the mobile device 800, including, for example, alithium-ion battery.

FIG. 14A is a schematic diagram of one embodiment of a packaged module900. FIG. 14B is a schematic diagram of a cross-section of the packagedmodule 900 of FIG. 14A taken along the lines 14B-14B.

The packaged module 900 includes radio frequency components 901, asemiconductor die 902, surface mount devices 903, wirebonds 908, apackage substrate 920, and encapsulation structure 940. The packagesubstrate 920 includes pads 906 formed from conductors disposed therein.Additionally, the semiconductor die 902 includes pins or pads 904, andthe wirebonds 908 have been used to connect the pads 904 of the die 902to the pads 906 of the package substrate 920.

The semiconductor die 902 includes a cascode power amplifier 945, whichcan be implemented in accordance with one or more features disclosedherein.

As shown in FIG. 14B, the packaged module 900 is shown to include aplurality of contact pads 932 disposed on the side of the packagedmodule 900 opposite the side used to mount the semiconductor die 902.Configuring the packaged module 900 in this manner can aid in connectingthe packaged module 900 to a circuit board, such as a phone board of awireless device. The example contact pads 932 can be configured toprovide radio frequency signals, bias signals, and/or power (forexample, a power supply voltage and ground) to the semiconductor die902. As shown in FIG. 14B, the electrical connections between thecontact pads 932 and the semiconductor die 902 can be facilitated byconnections 933 through the package substrate 920. The connections 933can represent electrical paths formed through the package substrate 920,such as connections associated with vias and conductors of a multilayerlaminated package substrate.

In some embodiments, the packaged module 900 can also include one ormore packaging structures to, for example, provide protection and/orfacilitate handling. Such a packaging structure can include overmold orencapsulation structure 940 formed over the packaging substrate 920 andthe components and die(s) disposed thereon.

It will be understood that although the packaged module 900 is describedin the context of electrical connections based on wirebonds, one or morefeatures of the present disclosure can also be implemented in otherpackaging configurations, including, for example, flip-chipconfigurations.

Although FIGS. 11A-14B illustrate examples of electronic systems thatcan include a cascode power amplifier implemented in accordance with theteachings herein, cascode power amplifiers can be used in otherconfigurations of electronics.

Applications

Some of the embodiments described above have provided examples inconnection with front end modules and/or wireless communication devices.However, the principles and advantages of the embodiments can be usedfor any other systems or apparatus that have needs for power amplifiers.

For example, power amplifiers can be included in various electronicdevices, including, but not limited to consumer electronic products,parts of the consumer electronic products, electronic test equipment,etc. Examples of the electronic devices can also include, but are notlimited to, memory chips, memory modules, circuits of optical networksor other communication networks, and disk driver circuits. The consumerelectronic products can include, but are not limited to, a mobile phone,a telephone, a television, a computer monitor, a computer, a hand-heldcomputer, a personal digital assistant (PDA), a microwave, arefrigerator, an automobile, a stereo system, a cassette recorder orplayer, a DVD player, a CD player, a VCR, an MP3 player, a radio, acamcorder, a camera, a digital camera, a portable memory chip, a washer,a dryer, a washer/dryer, a copier, a facsimile machine, a scanner, amulti-functional peripheral device, a wrist watch, a clock, etc.Further, the electronic devices can include unfinished products.

CONCLUSION

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Likewise, the word “connected”, as generally used herein, refers to twoor more elements that may be either directly connected, or connected byway of one or more intermediate elements. Additionally, the words“herein,” “above,” “below,” and words of similar import, when used inthis application, shall refer to this application as a whole and not toany particular portions of this application. Where the context permits,words in the above Detailed Description using the singular or pluralnumber may also include the plural or singular number respectively. Theword “or” in reference to a list of two or more items, that word coversall of the following interpretations of the word: any of the items inthe list, all of the items in the list, and any combination of the itemsin the list.

Moreover, conditional language used herein, such as, among others,“can,” “could,” “might,” “can,” “e.g.,” “for example,” “such as” and thelike, unless specifically stated otherwise, or otherwise understoodwithin the context as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements and/or states. Thus, such conditional language is notgenerally intended to imply that features, elements and/or states are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or withoutauthor input or prompting, whether these features, elements and/orstates are included or are to be performed in any particular embodiment.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A power amplifier system comprising: an inputterminal configured to receive a radio frequency input signal; an outputterminal; a cascode power amplifier including a plurality oftransconductance devices each electrically coupled to the inputterminal, and a plurality of cascode devices each electrically coupledto the output terminal, the plurality of transconductance devicesconfigured to operate in combination with the plurality of cascodedevices to amplify the radio frequency input signal; and a bias circuitconfigured to bias the plurality of cascode devices with two or morebias signals that are decoupled from one another at radio frequency soas to provide oscillation suppression to the cascode power amplifier. 2.The power amplifier system of claim 1 wherein the two or more biassignals include a plurality of bias voltages operable to separately biasthe plurality of cascode devices.
 3. The power amplifier system of claim2 further comprising two or more biasing conductors configured toseparately route the two or more bias signals to the plurality ofcascode devices, each of the two or more biasing conductors disconnectedfrom one another.
 4. The power amplifier system of claim 1 wherein thetwo or more bias signals includes a first bias voltage configured tobias a first portion of the plurality of cascode devices and a secondbias voltage configured to bias a second portion of the plurality ofcascode devices.
 5. The power amplifier system of claim 4 furthercomprising a radio frequency isolation circuit electrically coupledbetween the first bias voltage and the second bias voltage.
 6. The poweramplifier system of claim 1 wherein the plurality of transconductancedevices include a plurality of common emitter bipolar transistors, andthe plurality of cascode devices include a plurality of common basebipolar transistors.
 7. The power amplifier system of claim 1 whereinthe bias circuit includes a plurality of emitter follower bipolartransistors configured to bias the plurality of cascode devices with aplurality of bias voltages that are decoupled from one another at radiofrequency.
 8. The power amplifier system of claim 1 further comprising aplurality of degeneration circuits electrically coupled between theplurality of transconductance devices and ground.
 9. A packaged modulecomprising: a package substrate; and a semiconductor die attached to thepackage substrate, the semiconductor die including an input terminalconfigured to receive a radio frequency input signal, an outputterminal, and a cascode power amplifier including a bias circuit, aplurality of transconductance devices each electrically coupled to theinput terminal, and a plurality of cascode devices each electricallycoupled to the output terminal, the plurality of transconductancedevices configured to operate in combination with the plurality ofcascode devices to amplify the radio frequency input signal, and thebias circuit configured to bias the plurality of cascode devices withtwo or more bias signals that are decoupled from one another at radiofrequency so as to provide oscillation suppression to the cascode poweramplifier.
 10. The packaged module of claim 9 wherein the two or morebias signals include a plurality of bias voltages operable to separatelybias the plurality of cascode devices.
 11. The packaged module of claim10 wherein the semiconductor die further includes two or more biasingconductors configured to separately route the two or more bias signalsto the plurality of cascode devices, each of the two or more biasingconductors disconnected from one another.
 12. The packaged module ofclaim 9 wherein the two or more bias signals includes a first biasvoltage configured to bias a first portion of the plurality of cascodedevices and a second bias voltage configured to bias a second portion ofthe plurality of cascode devices.
 13. The packaged module of claim 12wherein the cascode power amplifier further includes a radio frequencyisolation circuit electrically coupled between the first bias voltageand the second bias voltage.
 14. The packaged module of claim 9 whereinthe plurality of transconductance devices include a plurality of commonemitter bipolar transistors, and the plurality of cascode devicesinclude a plurality of common base bipolar transistors.
 15. The packagedmodule of claim 9 wherein the bias circuit includes a plurality ofemitter follower bipolar transistors configured to bias the plurality ofcascode devices with a plurality of bias voltages that are decoupledfrom one another at radio frequency.
 16. The packaged module of claim 9wherein the bias circuit is further configured to bias the plurality oftransconductance devices with a common bias signal.
 17. The packagedmodule of claim 9 wherein the cascode power amplifier further includes aplurality of degeneration circuits electrically coupled between theplurality of transconductance devices and ground.
 18. A wirelesscommunication device comprising: a transmitter configured to generate aradio frequency signal; a cascode power amplifier system including aninput terminal configured to receive the radio frequency signal, anoutput terminal, a bias circuit, a plurality of transconductance deviceseach electrically coupled to the input terminal, and a plurality ofcascode devices each electrically coupled to the output terminal, theplurality of transconductance devices configured to operate incombination with the plurality of cascode devices to amplify the radiofrequency signal to thereby generate an amplified radio frequencysignal, and the bias circuit configured to bias the plurality of cascodedevices with two or more bias signals that are decoupled from oneanother at radio frequency so as to provide oscillation suppression; andan antenna configured to receive the amplified radio frequency signal.19. The wireless communication device 18 wherein the two or more biassignals include a plurality of bias voltages operable to separately biasthe plurality of cascode devices.
 20. The wireless communication device18 wherein the plurality of transconductance devices include a pluralityof common emitter bipolar transistors, and the plurality of cascodedevices include a plurality of common base bipolar transistors.